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180.

Problem 2.40 (R)

A stick at rest in S has a length L and is inclined at angle to the x-axis. We have to find its length and angle of inclination to the axis as measured by an observer in moving with a speed v relative to x along the axes.

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In the inertial frame S the rod is at rest. Its length measured in S is L. The x and y components of the length of the rod in frame S are

where as shown in the diagram the rod is inclined at angle with respect to x-axis.

The inertial frame is moving with speed V in the direction of x-axis as measured by S. Let the length of the rod measured by be and the inclination of the rod with respect to axis be by an angle . Its components measured by will be

By Lorentz transformations we note that

The length will therefore be

And